Chemistry | 2019
Polarity Induced Excited-State Intramolecular Proton Transfer (ESIPT) in a Pair of Supramolecular Isomeric Multifunctional Dynamic Metal-Organic Framework.
Abstract
A pair of supramolecular isomer of Cd(II) MOF has been synthesized utilizing one flexible N,N -donor linker and a dicarboxylate with ESIPT (excited-state intramolecular proton transfer) fluorophore by differing the reaction media. One of them has 3D fourfold interpenetrated framework with guest solvent in the structure, which shows excellent solvent dependent crystalline-to-crystalline structural transformation that have been extensively studied by PXRD and IR spectroscopy. The other one is structurally rigid in nature and has a twofold interpenetrated structure without any guest molecule. Both the compounds show moderate CO2 adsorption and one of them, having fourfold interpenetrated structure shows moderately high H2 adsorption as well. Furthermore, both the compounds show interesting luminescence behavior. In solid state, these compounds show single peak spectra whereas on suspension of these compounds in polar solvents, the maxima split into two peaks with a huge Strokes shift. On the other hand, in non-polar solvents there is only one emission maxima has been found. This solvatochromic dual-emission phenomenon is due to the excited-state intramolecular proton transfer which has been extensively studied.